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  • Industrial Waste Water Treatment - IWWT
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UNIT- I Sources of Industrial Waste Industrial wastewater means used up water from industries. The characteristics of waters depend on the nature of industry. Sources of Industrial Waste Water Agricultural Waste The agricultural sector produces an enormous volume of wastewater every year. The two main sources of wastewater in agriculture are: a) non-point source pollution and b) point source pollution. Non point source pollution is generally a result of surface run offs from fields, especially during periods of excessive rainfall, whereas point source pollution in agriculture is a localized source constituting animal waste, treatment, piggery waste, firewater, silage liquor, milking parlor wastes, slaughtering wastes and vegetable washing wastes. Run offs in non point source may also include nutrients, pesticides and soil sediments that cause high levels of turbidity in water bodies, encouraging the growth of aquatic plants, clog fish gills and smother animal. 2

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Iron & Steel Industry The iron and steel industry consumes water mainly for cooling, washing, gas transfer, matter removal, etc. Right from the mining process to the fabrication of steel, the entire iron and steel manufacturing process incorporates powerful reduction reactions in blast furnaces. The water used for cooling is therefore begrimed by chemicals such as ammonia and cyanide. Contamination of waste streams includes gasification products such as benzene, naphthalene, cyanide, ammonia, phenols and cresols, along with a wide array of more composite organic compounds collectively known as polycyclic aromatic hydrocarbons (PAH). Even during other stages, e.g., in the final treatment stage where pickling is done in strong mineral acids for rust removal and preparing the surface for surface treatments such as galvanization or painting, large amount of water is generated which is contaminated by acids like hydrochloric acid and sulfuric acid. Mines & Quarries Contaminants of mining and quarrying consist mainly of slurries of rock particles that arise mainly from rainfall washing exposed surfaces and haul roads. At times, they are also formed during rock washing and grading processes. These inert contaminants are abundantly generated during the extraction and on-site processing of materials such as coal, china clay, slate, metalliferous and vein materials. Although the waste generated is normally chemically inert and stable enough to be easily deposited on the land without pre-treatment, it has to be noted that some waste may contain high levels of metals that can have a harmful effect on wildlife and plants. Oils and hydraulic oils are also common contaminants of mine and quarry waste water. Complex Organic Chemicals Industry Chemical pollutants include a wide variety of contaminants ranging from simple inorganic ions to complex organic molecules. Organic compounds that are dangerous to the environment are all man-made and have only existed during the last century. Apart from the organic chemical manufacturing plants, a lot of other industries also work with complex organic compounds regularly. These include pesticides, pharmaceuticals, paints and dyes, petro-chemicals, detergents, plastics, paper pollution, etc. These industries generally deteriorate the quality of water by contaminating it with feed-stock materials, by3

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products, product material in soluble or particulate form, washing and cleaning agents, solvents and added value products. Nuclear Industry One of the most water-intensive sectors, the nuclear industry requires large amounts of water every day, mainly for cooling purposes. The hot-water outflows, contaminated with radioactive chemicals after being used in various processes is pumped back to rivers, lakes and oceans, which poses serious environmental threats. The production of these radio active contaminants in nuclear-power plants mainly takes place during the mining and refining stage of uranium and thorium and the fission reaction involved in the production process. In nuclear fuel cycle, the front end usually produces alpha-emitting waste from the extraction of uranium. It often contains radium and its decay products. The back end, mostly spent fuel rods, contains fission products that emit beta and gamma radiation, and actinides that emit alpha particles, such as uranium-234, neptunium-237, plutonium-238 and americium-241, and even sometimes some neutron emitters such as californium (Cf). Food Industry Wastewater generated in the food industry though biodegradable and nontoxic, contains high concentrations of biochemical oxygen demand (BOD) and suspended solids (SS). Typically, vegetable washing and animal slaughter and processing generates waste water that is packed with high loads of particulate matter (PM) and dissolved organics. Animal slaughter and processing also lead to the production of strong organic waste, which are derived from body fluids, including gut contents and blood. This wastewater also contains pollutants like antibiotics, growth hormones, and at times pesticides, which come from the animal body. Even, food processing and cooking generates large to trace amounts of salt, flavorings, coloring material, acids, alkali, oil or fats. Generally pollution properties are: Physical pollution - Temperature, Colour, Odour, Taste ,Solids Chemical pollution - pH, Acidity, Dissolved salts Organic pollution - Organic Matter Biological pollution - Biological Activities 4

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